1. Field of the Invention
This invention relates to an ink jet recording head, and more particularly this invention relates to an ink jet recording head which produces recording ink droplets for so-called ink jet recording system.
2. Description of the Prior Art
An ink jet recording head used for an ink jet recording system is usually provided with fine ink discharging outlets (orifices), ink pathways, and ink discharging pressure generating portion in the ink pathway.
There are previously known as methods for fabricating an ink jet recording head. For example procedure of cutting or etching a glass or metal plate to form fine grooves and binding it to a plate to form ink pathways.
However, the ink discharging characteristics of the ink jet recording head made by such conventional procedures are liable to fluctuate because of excessive roughness of the internal walls of the ink pathways made by cutting or distortions in the ink pathways due to the differences of the etching degree and because of the difficulty of maintaining a constant flow resistance of the pathways. There are also drawbacks that the plates are liable to be chipped off or broken during the cutting process, resulting in low fabrication yields of the ink jet recording heads. And further, the conventional etching methods have common shortcomings of the lack of mass productivity because of the difficulty of registering the grooved plate and the cover plate equipped with driving elements such as piezoelectric elements and heating elements and the like, where they are bonded together.
In order to overcome these shortcomings, there have been proposed a constitution of an ink jet recording head, for example, in Japanese laid-open patent Appln. No. 43876/1982 wherein ink pathways are formed from cured photosensitive resin film on a substrate equipped with pressure-generating elements for ink discharge and then a cover is placed on said ink pathways.
The fabrication of the ink jet recording head by utilizing photosensitive resin is superior to conventional fabrication process because it overcomes such shortcomings of the conventional ink heads as the lack of finishing accuracy of the ink pathways, the complexity of the fabrication process, and low yield. Yet there still remains a problem of insufficient bonding between the substrate having the pressure elements for ink discharge and the pathway walls formed from a cured photosensitive resin film on a substrate. In other words, too large shrinking stress formed in the cured photosensitive film causes insufficient adhesion of the pathway wall onto the substrate, leading to frequent occurrence of peeling-off of the pathway formed on the substrate after the head is completed.
There are provided elements for generating ink discharging pressure and electric wires for transmitting electric signals thereto, and an electric insulating layer and an ink-resistant layer are laminated thereon, but the constriction stress in the ink pathway of the cured photosensitive resin film is so large that peeling-off of the electric insulating layer or ink-resistant layer from the substrate often occur besides that of the ink-pathway itself.